Unity 3d 在两个对象之间传递 bool 变量

Question

how i can pass a simple boolean variable between two different object? I can try this but didn't work...

First script:

  public class CollisionController : MonoBehaviour
{
    public PlayerMovement movement;
    public bool active = false;



    private void OnCollisionEnter(Collision collision)
    {
        if(collision.collider.tag == "Obstacle")
        {
            active = true;
        }
    }
}

Second script (that read the boolean variable "active")

   public class EmptyControllerColl : MonoBehaviour
{
    public CollisionController controller;
    public PlayerMovement movement;

    public bool activeLocal = false;

    private void Start()
    {
        GetComponentInChildren<CollisionController>();
    }
    void Update()
    {


        activeLocal = controller.active;

        if(activeLocal == false)
        {
            Debug.Log("Nothing...");
        }

        if(activeLocal == true)
        {
            Debug.Log("Game over");

        }
    }
}

When the variable bool "Active" change its status, the variable "activeLocal" don't change status.. How can I resolve this problem?

Collision Controller is "connect" to Cube Object.

EmptyControllerColl is "connect" to emptyGameObject (parent of Cube).

Answer 1

This line

_ = GameObject.Find("cubo Variant").GetComponent<CollisionController>().active;

makes no sense. First of all there is no field or variable declared with the name _ so this shouldn't even compile at all. And secondly what do you need this for? Rather store the according reference once in the controller field and reuse it later.

Then for your usecase there is no need at all to store the value in a local variable ... this makes things only more complicated. Simply where you need it get the value from controller.active .

Also do not use == for tags. Rather check via CompareTag . The problem is that == silently fails if you have any typo or the tag doesn't exist at all. CompareTag rather throws an error that the given tag is not valid.

public class EmptyControllerColl : MonoBehaviour
{
    // Best already drag this in via the Inspector in Unity
    [SerializeField] private CollisionController controller;
    public PlayerMovement movement;

    // As fallback get it ONCE on runtime
    private void Awake()
    {
        // since you say the cube is a child of this empty object you do not use
        // Find at all but can simply use GetComponentInChildren
        if(!controller) controller = GetComponentInChildren<CollisionController>(true);
    }

    void Update()
    {
        // No need to store this in a local field at all
        if(!controller.active)
        {
            Debug.Log("Nothing...");
        }
        // use if else since both cases are exclusive and you don't even need to check the value twice
        else 
        {
            Debug.Log("Game over");
        }
    }
}

---

Event Driven - part A

In general you should avoid poll checks for a bool value in Update and rather come up with a more event driven solution! An example could look like:

public class CollisionController : MonoBehaviour
{
    public PlayerMovement movement;

    // Here everyone who wants can add listeners that get called as soon as
    // we invoke this event. We will do it everytime the 'active' value is changed
    public event Action<bool> OnActiveStateChanged;

    // Backing field for 'active'
    private bool _active;

    // Property that reads and writes '_active'
    // Everytime it is assigned it also invokes 'OnActiveStateChanged'
    private bool active
    {
        get { return _active; }
        set
        {
            _active = value;
            OnActiveStateChanged?.Invoke(_active);
        }
    }

    private void OnCollisionEnter(Collision collision)
    {
        if(collision.collider.CompareTag("Obstacle"))
        {
            active = true;
        }
    }
}

Now you would register a listener for this event like

public class EmptyControllerColl : MonoBehaviour
{
    // Best already drag this in via the Inspector in Unity
    [SerializeField] private CollisionController controller;
    public PlayerMovement movement;

    // As fallback get it ONCE on runtime
    private void Awake()
    {
        // since you say the cube is a child of this empty object you do not use
        // Find at all but can simply use GetComponentInChildren
        if(!controller) controller = GetComponentInChildren<CollisionController>(true);

        // register a callback. It is allowed an save to unregister first
        // which makes sure this is only registered exactly once
        controller.OnActiveStateChanged -= HandleControlerActiveStateChanged;
        controller.OnActiveStateChanged += HandleControlerActiveStateChanged;
    }

    private void HandleGameOver()
    {
        Debug.Log("Game over");
    }

    private void HandleControlerActiveStateChanged(bool value)
    {
        if(!value)
        {
            Debug.Log("Nothing...");
        }
        else 
        {
            Debug.Log("Game over");
        }
    }

    private void OnDestroy()
    {
         // always clean up listeners
         controller.OnActiveStateChanged -= HandleControlerActiveStateChanged;
    }
}

This now is way more efficient since you don't all time run an Update method. Instead the HandleControlerActiveStateChanged is only called when the value of active is actually changed.

---

Event Driven - part B

And then actually in your case there is need to use a bool at all you could use a simple event Action instead and remove all the bools entirely:

public class CollisionController : MonoBehaviour
{
    public PlayerMovement movement;

    public event Action OnGameOver;

    private void OnCollisionEnter(Collision collision)
    {
        if(collision.collider.CompareTag("Obstacle"))
        {
            OnGameOver?.Invoke();
        }
    }
}

Now you would register a listener for this event like

public class EmptyControllerColl : MonoBehaviour
{
    [SerializeField] private CollisionController controller;
    public PlayerMovement movement;

    private void Awake()
    {
        if(!controller) controller = GetComponentInChildren<CollisionController>(true);

        controller.OnGameOver -= HandleGameOver;
        controller.OnGameOver += HandleGameOver;
    }

    private void HandleGameOver()
    {
        Debug.Log("Game over");
    }

    private void OnDestroy()
    {
        controller.OnGameOver -= HandleGameOver;
    }
}

Answer 2

using UnityEngine;

public class CollisionController : MonoBehaviour
{
    void Start()
    {
        // Calls the function ApplyDamage with a value of 5
        // Every script attached to the game object
        // that has an ApplyDamage function will be called.
        gameObject.SendMessage("ApplyDamage", 5.0);
    }
}

public class EmptyControllerColl : MonoBehaviour
{
    public void ApplyDamage(float damage)
    {
        print(damage);
    }
}

https://docs.unity3d.com/ScriptReference/GameObject.SendMessage.html